I did not write anything about English so far and have few things to add. But English is far easier than any other languages I know of, since I have very low standard. Also there are a plenty of good books on English unlike on Dutch. It is nearly impossible to learn Dutch in the way I want to learn since there are so few books about learning Dutch.
It seems that a lot of Japanese think people in other countries are better at English than Japanese. But I do not know this is true or not.
You can improve language skill in any languages till you die. I did not have any preconception on how long it will take me to learn English. Rather, I was more interested in understanding and research. The concept and idea are ingrained into brain directly; particularly in physics and mathematics.
Time frame of the improvement of my English went like this.
1) 3 years made my English level that of a 10 years old native.
2)5 years made my English level that of a 16 years old.
3)7 years made my English level that of a 19 years old.
4)10 years made my English level that of a 21 years old.
5)13 years made my English level that of a 26 years old.
6)16 years made my English level that of my brain.
So I do not have any advice nor tricks to quickly acquire English. I did listen to BBC, VOA and Christian Science Monitor radios and many TOEIC and other tapes when I was in Japan. I did went to ESL at UC Davis. It was an extremely useful experience to find out that an ESL is useless for me and to find that there is absolutely no easy way to learn a language. I probably do not have any good literature brain in any languages not systematic writing.